Driveline assemblies are a type of power take off assembly that transfers torque loads from a driving member to a driven member. The driveline assembly usually has a universal joint at each end. The typical cardan type universal joint is basically made up of two yokes each connected to a single center cross with four needle bearings. A fixed driveline assembly is used in applications where the required length of assembly does not vary such as power steering unit. A slip type or telescoping assembly is designed for applications in which the length of the assembly may vary during its normal operation because of application movement or function such as driveline connections between tractors and farming implements in agricultural applications. Typical inter-axle slip type driveline assemblies can operate up to a 45.degree. angle and can have length variations from 12 to over 50 inches.
Agricultural slip type driveline assemblies are generally of a sliding shaft design. A square shaft is fitted into a square tube slip yoke having an internal cavity that generally mates with the square shaft. The square shaft is generally welded to the square hole yoke. Universal joint assemblies are attached to each yoke completing the assembly. The square cavity within the square tube slip yoke generally contains lubricants and is sealed by a plug and a seal which keeps the lubricant in and contaminants out. Although the cross sectional geometry of the slip yoke and shaft are generally square, other configurations such as hexagonal cross sections can be used. In addition, while the square slip yoke and shaft of some agricultural driveline maintains their square cross section over their entire length, some units have a transitional area where the square cross section is modified into a circular cross section.
The seal is generally one of two types: multi-component or one piece. With multiple-component seals, one or more split washers with internal splines are positioned over the end of the slip yoke and held in place by a metal dust cap. The washer sets are usually of metal and cork or nylon and felt construction. With single piece construction, the dust cap is generally rubber and is fitted over the end of a slip yoke. The outer surface of a portion of the seal is generally bonded to a metal band that helps maintain the overall seal geometry and keeps the seal in place.